Lactobacillus rhamnosus CRL981 INCREASES ANTIOXIDANT CAPACITY IN FERMENTED SOYBEAN ENRICHED WITH BIOACTIVE AGLYCONES

MARAZZA J.; NAZARENO M.A.; GARRO M.S.; SAVOY DE GIORI G.

San Miguel de Tucumán, Tucumán, Argentina

Simposio; III Simposio Internacional de Bacterias Lacticas; 2009

CERELA-CONICET

Free radicals and other reactive oxygen species, generated by exogenous chemicals or endogenous metabolic processes in food systems or the human body, may cause oxidative damage playing significant pathological role in aging process and age-related human diseases. The ingestion of antioxidative supplements or antioxidant-containing foods may reduce oxidative damage in the human body. The continuous search for new products from traditional raw material and processes that provide ingredients with new functionalities and cost-effective manufacturing is the main goal of the food industry. Soybeans are known for their potential bioactive antioxidant properties attributed to isoflavones (IS) content. In this substrate, IS are found as glucoside conjugates being less bioactive than their respective aglycones. Some lactic acid bacteria strains with beta-glucosidase activity are able to hydrolyze beta-glucosides. The aim of our study was to examine whether levels of both total antioxidant activity and bioactive IS aglycones increased in fermented soymilk with beta-glucosidase-producing L. rhamnosus CRL981. Soymilk was inoculated (4% v/v) with this strain and allowed to ferment at 37ºC for 24 h. Samples were aseptically withdrawn at 0, 3, 6, 9, 12 and 24 h to determine IS by HPLC and total soluble phenolic content using Folin Ciocalteu assay. The antiradical activity, expressed as a percentage of antiradical activity (% ARA), was determined spectrophotometrically using DPPH radical. At the end of fermentation glucosides IS were hydrolyzed (54.7% of daidzin and 100% of genistin) by beta-glucosidase activity. Total phenolic content did not change (106.2 microg of galic acid equivalents/ml) along soymilk fermentation; however free radical scavenging activity of soymilk increased reaching the value of 41.8% ARA at 24 h of fermentation. These results evidence that aglycones IS were responsible for the DPPH scavenging activity detected in this study. L. rhamnosus CRL981 could be used as starter culture for processed soy products enriched in aglycones IS with beneficial effects to consumers.